This invention generally concerns automotive multicylinder internal combustion engines and particularly to apparatus for selectively shutting off one or more cylinders of the engine when reduced power output can operate the vehicle adequately.
Nowadays, automotive engineers and manufacturers are greatly interested in the technology of controlling fuel supply to some of the engine cylinders for the sake of world-wide requirement for fuel economy. They have already proposed several types of apparatus which incorporate this technology by disabling or deactivating the intake and exhaust valves of the corresponding cylinders when required. Especially for a carburetor-controlled engine, there is known a mechanical device for such deactivation which collapses or locks a hydraulic valve lifter in a position in which the intake or exhaust valve is kept shut off in any angular position of a camshaft. The device per se is actuated from an electric and electronic control apparatus responsive to one or more engine parameters.
This type of device is however not applicable to an overhead cam type engine lacking any hydraulic lifter. Besides, since locking of a hydraulic lifter is mostly accomplished by mechanical means common to all the cylinders, the number and the combination of inactive cylinders can not be altered in dependence on engine power requirement.
It is therefore a general object of this invention to provide an apparatus to cut off fuel delivery to one or more cylinders of a multi-cylinder engine by deactivating intake and exhaust valves of the corresponding cylinders when the total amount of fuel required for the engine in a particular operation mode is relatively small, thus minimizing fuel consumption.
Another object of this invention is to provide an apparatus of the aforementioned type which is designed and constructed for use with an overhead cam type engine in which cam lobes act on the intake and exhaust valves to lift them only through stud-mounted rocker arms.
Still another object of this invention is to provide an apparatus of the aforementioned type in which the number and the combination of the inactive cylinders can be altered at will in accordance with engine power requirement.
A further, more specific object of this invention is to provide an apparatus of the aforementioned type in which a floating stud for the rocker arm is hydraulically operated to move between a normally operating position and a locking position in which the engine valves are deactivated.
Other objects of this invention are a simple structure without any important modification of the engine in use, and therefore reduced manufacturing cost.